Pycnogenol originally denoted all proanthocyanidin extracts, regardless of source. However, it now refers specifically to maritime pine bark. The mixture of proanthocyanidins in pine bark supports vascular endothelial integrity by stabilizing collagenous membranes. They also promote vascular function by modulating nitric oxide levels. In addition to facilitating vitamin C regeneration and preserving vitamin E, pycnogenol is a potent hydroxyl and superoxide radical scavenger. Collectively, these actions promote the health of blood vessels. Pycnogenol contains a minimum of 65-75% proanthocyanidins by weight.